TW202008567A - Methods for forming three-dimensional memory devices - Google Patents

Abstract

Embodiments of methods for forming three-dimensional (3D) memory devices are disclosed. In an example, a peripheral device is formed on a first substrate. A first interconnect layer is formed above the peripheral device on the first substrate. A dielectric stack including a plurality of dielectric/sacrificial layer pairs and a plurality of memory strings each extending vertically through the dielectric stack is formed on a second substrate. A second interconnect layer is formed above the memory strings on the second substrate. The first substrate and the second substrate are bonded, so that the first interconnect layer is below and in contact with the second interconnect layer. The second substrate is thinned after the bonding. A memory stack is formed below the thinned second substrate and including a plurality of conductor/dielectric layer pairs by replacing, with a plurality of conductor layers, sacrificial layers in the dielectric/sacrificial layer pairs.

Description

Method for forming three-dimensional memory device

Embodiments of the present disclosure relate to three-dimensional (3D) memory devices and methods of manufacturing the same.

By improving process technology, circuit design, programming algorithms and manufacturing processes, the planar storage unit is scaled to a smaller size. However, as the feature size of the storage unit approaches the lower limit, planar manufacturing processes and manufacturing techniques become challenging and costly. As a result, the storage density of the planar storage unit approaches the upper limit.

The 3D memory architecture can solve the density limitation in planar storage units. The 3D memory architecture includes a storage array and peripheral devices for controlling signals entering and exiting the storage array.

Disclosed herein is an embodiment of a method for forming a 3D memory device.

In one example, a method for forming a 3D memory device is disclosed. The peripheral device is formed on the first substrate. A first interconnect layer is formed on the peripheral device on the first substrate. A dielectric stack layer including a plurality of dielectric/sacrificial layer pairs and a plurality of memory strings is formed on the second substrate, and each memory string extends vertically through the dielectric stack layer. A second interconnect layer is formed on the memory string on the second substrate. The first substrate and the second substrate are bonded so that the first interconnect layer is below and in contact with the second interconnect layer. After bonding, the second substrate is thinned. By replacing the sacrificial layer in the dielectric/sacrificial layer pair with a plurality of conductor layers, the storage stack layer is formed under the thinned second substrate and includes a plurality of conductor/dielectric layer pairs.

In another example, a method for forming a 3D memory device is disclosed. The peripheral device is formed on the first substrate. A first interconnect layer is formed on the peripheral device on the first substrate. A plurality of memory strings each extending vertically are formed on the second substrate. A second interconnect layer is formed on the memory string on the second substrate. The first substrate and the second substrate are bonded so that the first interconnect layer is below and in contact with the second interconnect layer. After bonding, the second substrate is thinned. The storage stack layer is formed under the thinned second substrate and includes a plurality of conductor/dielectric layer pairs. In the stepped structure of the storage stack layer, the edges of the conductor/dielectric layer pair along the vertical direction away from the first substrate are laterally staggered toward the memory string.

In yet another example, a method for forming a 3D memory device is disclosed. A plurality of memory strings each extending vertically are formed on the substrate. An interconnect layer is formed on the memory string. Turn the substrate upside down so that the substrate is above the memory string. After turning over, the substrate is thinned. After thinning, the storage stack layer is formed under the thinned substrate and includes a plurality of conductor/dielectric layer pairs. A plurality of first via contacts are formed such that each first via contact is above and in contact with the conductor layer of one conductor/dielectric layer pair of the conductor/dielectric layer pair.

Although specific configurations and arrangements have been discussed, it should be understood that this is for exemplary purposes only. Those skilled in the relevant art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the present disclosure. It will be apparent to those skilled in the relevant art that the present disclosure can also be used in a variety of other applications.

It should be noted that references to "one embodiment", "embodiments", "exemplary embodiments", "some embodiments", etc. in the specification indicate that the described embodiments may include specific features, structures or characteristics, but Not every embodiment includes this particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. In addition, when a specific feature, structure, or characteristic is described in conjunction with an embodiment, it should be within the knowledge of those skilled in the relevant art to implement such feature, structure, or characteristic in combination with other embodiments (whether or not explicitly described).

Generally, terminology can be understood at least in part from use in context. For example, depending at least in part on the context, the term "one or plural" as used herein may be used to describe features, structures, or characteristics in the singular, or may be used to describe combinations of features, structures, or characteristics in the plural. Similarly, depending at least in part on the context, terms such as "a" or "said" may be understood to convey singular or plural usage. In addition, the term "based on" may be understood as not necessarily intended to convey a set of exclusive factors, but may instead, depending at least in part on the context, allow other factors that are not necessarily explicitly described.

It should be easily understood that the meanings of "on", "above", and "above" in this disclosure should be interpreted in the broadest way so that "on" not only means "directly on" "On" also includes "on" something with intervening features or layers in between, and "above" or "above" not only means "above" or "above" The meaning of "" may also include the meaning of "over" or "above" something without intervening features or layers (ie, directly on something).

In addition, space-related terms such as “below”, “below”, “lower”, “above”, “upper”, etc. are used herein to describe an element or feature and another for convenience of description The relationship of one or more elements or features is shown in the drawings. Spatially related terms are intended to cover different orientations in the use or operation of the device than those depicted in the drawings. The device can be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially related descriptors used herein can be similarly interpreted accordingly.

As used herein, the term "substrate" refers to a material on which subsequent materials are added. The substrate itself can be patterned. The material added on top of the substrate may be patterned or may remain unpatterned. In addition, the substrate may include a wide range of semiconductor materials, such as silicon, germanium, gallium arsenide, indium phosphide, and the like. Alternatively, the substrate may be made of a non-conductive material such as glass, plastic or sapphire wafer.

As used herein, the term "layer" refers to a portion of material that includes regions with thickness. The layer can extend over the entirety of the underlying or superstructure, or can have a range that is less than the extent of the underlying or superstructure. In addition, the layer may be a region of a homogeneous or heterogeneous continuous structure with a thickness less than that of the continuous structure. For example, the layer may be located between the top and bottom surfaces of the continuous structure or between any horizontal faces at the top and bottom surfaces. The layer can extend horizontally, vertically or/and along inclined surfaces. The substrate may be a layer, which may include one or more layers, or/and may have one or more layers on, above, and/or below it. The layer may include a plurality of layers. For example, the interconnect layer may include one or more conductors and contact layers (where interconnect lines or/and via contacts are formed) and one or more dielectric layers.

As used herein, the term “nominal/nominally” refers to a desired or target value for a characteristic or parameter of a component or process operation set during the design phase of production or process, and above or/and below expected value Range of values. The range of values may be due to slight changes in the manufacturing process or tolerances. As used herein, the term "approximately" indicates a given amount of value that may vary based on the specific technology node associated with the subject semiconductor device. Based on a particular technology node, the term "about" may indicate a given amount of value, which varies, for example, within 10%-30% of the value (eg, ±10%, ±20%, or ±30% of the value).

As used herein, the term "3D memory device" refers to a string of memory cell transistors having a vertical orientation on a laterally oriented substrate (referred to herein as a "memory string", such as a NAND memory string) A semiconductor device that makes the memory string extend in a vertical direction with respect to the substrate. As used herein, the term "vertically/vertically" means nominally orthogonal to the lateral surface of the substrate.

Compared with other 3D memory devices, various embodiments according to the present disclosure provide a method for forming a 3D memory device having a smaller grain size, higher cell density, and improved performance. By vertically stacking storage array element wafers on peripheral device wafers, the cell density of the resulting 3D memory device can be increased. Furthermore, by decoupling peripheral device processing from storage array element processing, the thermal budget associated with processing the storage array element is not limited by the performance requirements of the peripheral device. Similarly, peripheral device performance is not affected by storage array element processing. For example, peripheral devices and storage array elements can be fabricated on different substrates, respectively, so that certain high-temperature processes used to manufacture storage array elements do not adversely affect the manufacture of peripheral devices (eg, to avoid excessive diffusion of dopants, Control the doping concentration or thickness of ion implantation, etc.).

FIG. 1 shows a cross-section of an exemplary 3D memory device 100 according to some embodiments of the present disclosure. The 3D memory device 100 represents an example of a non-monolithic 3D memory device. The term “non-monolithic” means that elements of the 3D memory device 100 (eg, peripheral devices and storage array elements) may be formed separately on different substrates and then connected to form the 3D memory device. The 3D memory device 100 may include a substrate 102, which may include silicon (eg, single crystal silicon), silicon germanium (SiGe), gallium arsenide (GaAs), germanium (Ge), silicon on insulator (SOI) or Any other suitable material.

The 3D memory device 100 may include peripheral devices on the substrate 102. The peripheral device may be formed "on" the substrate 102, wherein the entirety or part of the peripheral device is formed in the substrate 102 (eg, below the top surface of the substrate 102) or/and directly formed on the substrate 102. The peripheral device may include a plurality of transistors 104 formed on the substrate 102. Isolation regions (eg, shallow trench isolation (STI), not shown) and doped regions (eg, source and drain regions of the transistor 104, not shown) may also be formed in the substrate 102.

In some embodiments, the peripheral devices may include any suitable digital, analog, and/or mixed signal peripheral circuits for facilitating the operation of the 3D memory device 100. For example, the peripheral device may include one or more page buffers, decoders (eg, row decoders and column decoders), sense amplifiers, drivers, charge pumps, current or voltage reference sources, or any active or passive circuits Components (for example, transistors, diodes, resistors, or capacitors). In some embodiments, complementary metal oxide semiconductor (CMOS) technology (also referred to as a “CMOS wafer”) is used to form peripheral devices on the substrate 102.

The 3D memory device 100 may include an interconnect layer above the transistor 104 (referred to herein as a “peripheral interconnect layer 106 ”) to transmit electrical signals to and from the transistor 104. The peripheral interconnect layer 106 may include a plurality of interconnects (also referred to herein as “contacts”), including horizontal interconnect lines 108 and vertical interconnect access (through-hole) contacts 110. As used herein, the term "interconnect" can broadly include any suitable type of interconnect, such as mid-end process (MEOL) interconnect and back-end process (BEOL) interconnect. The peripheral interconnect layer 106 may also include one or more interlayer dielectric (ILD) layers (also referred to as “inter-metal dielectric (IMD) layers”) in which interconnect lines 108 and via contacts 110 may be formed. That is, the peripheral interconnect layer 106 may include a plurality of interconnect lines 108 and via contacts 110 in the ILD layer. The interconnection line 108 and the via contact 110 in the peripheral interconnection layer 106 may include conductive materials, including but not limited to tungsten (W), cobalt (Co), copper (Cu), aluminum (Al), silicide, or Any combination of them. The ILD layer in the peripheral interconnect layer 106 may include dielectric materials including, but not limited to, silicon oxide, silicon nitride, silicon oxynitride, low dielectric constant (low-k) dielectric materials, or any combination thereof.

In some embodiments, the peripheral interconnect layer 106 also includes a plurality of bonding contacts 112 at the top surface of the peripheral interconnect layer 106. The bonding contact 112 may include a conductive material, including but not limited to W, Co, Cu, Al, silicide, or any combination thereof. The remaining area at the top surface of the peripheral interconnect layer 106 may be formed with a dielectric material, including but not limited to silicon oxide, silicon nitride, silicon oxynitride, low-k dielectric material, or any combination thereof. The conductive material (of the bonding contact 112) and the dielectric material at the top surface of the peripheral interconnect layer 106 can be used for hybrid bonding, as described in detail below.

The 3D memory device 100 may include a storage array element on the peripheral device. Please note that the x-axis and the y-axis are included in the first figure to further illustrate the spatial relationship of the elements in the 3D memory device 100. The substrate 102 includes two lateral surfaces (for example, a top surface and a bottom surface) extending laterally in the x direction (ie, the lateral direction or the width direction). As used herein, whether an element (eg, layer or element) is "on", "over", or "of" another element (eg, layer or element) of a semiconductor device (eg, 3D memory device 100) "Down" is determined in the y direction (ie, the vertical direction or thickness direction) relative to the substrate of the semiconductor device (for example, the substrate 102) when the substrate is located in the lowest plane of the semiconductor device in the y direction . The same concepts used to describe spatial relationships are used throughout this disclosure.

In some embodiments, the 3D memory device 100 is a NAND flash memory device, in which the storage unit is provided in the form of an array of NAND memory strings 114, and each NAND memory string 114 is in a peripheral device (eg, transistor 104 ) Extends vertically above the substrate 102. The storage array element may include a NAND memory string 114 that extends vertically through a plurality of pairs, each pair including a conductor layer 116 and a dielectric layer 118 (referred to herein as "conductor/dielectric layer pair"). The stacked conductor/dielectric layer pairs are also referred to herein as "storage stack layers" 120. The conductor layer 116 and the dielectric layer 118 in the storage stack layer 120 alternate in the vertical direction. In other words, in addition to the conductor/dielectric layer pair at the top or bottom of the storage stack layer 120, each conductor layer 116 may be adjacent to two dielectric layers 118 on both sides, and each dielectric layer 118 The two conductor layers 116 may be adjacent on both sides. The conductor layers 116 may each have the same thickness or different thicknesses. Similarly, the dielectric layers 118 may each have the same thickness or different thicknesses. The conductor layer 116 may include a conductor material, including but not limited to W, Co, Cu, Al, doped silicon, silicide, or any combination thereof. The dielectric layer 118 may include a dielectric material, including but not limited to silicon oxide, silicon nitride, silicon oxynitride, or any combination thereof.

The storage stack layer 120 may include an inner area (also referred to as a “core array area”) and an outer area (also referred to as a “step area”). In some embodiments, the inner area is the central area of the storage stack layer 120 in which an array of NAND memory strings 114 is formed, and the outer area is the remaining area (including sides and edges) of the storage stack layer 120 surrounding the inner area. As shown in FIG. 1, at least on one side, the outer region of the storage stack layer 120 may include a stepped structure 122. The edges of the conductor/dielectric layer pairs in the vertical structure (positive y direction) away from the substrate 102 in the stepped structure 122 of the storage stack layer 120 are laterally staggered toward the array of NAND memory strings 114. In other words, the edge of the storage stack layer 120 in the stepped structure 122 may be inclined toward the inner area as it moves away from the substrate 102 (from the bottom to the top). The slope of the step structure 122 may face away from the substrate 102. In some embodiments, the length of each conductor/dielectric layer pair of the storage stack 120 increases from top to bottom.

In some embodiments, every two adjacent conductor/dielectric layer pairs in the stepped structure 122 are offset by a nominally the same distance in the vertical direction and by a nominally the same distance in the lateral direction. Therefore, each offset can form a "landing area" for the fan-out of word lines in the vertical direction. Some conductor layers 116 of the conductor/dielectric layer pair can be used as word lines of the 3D memory device 100 and extend laterally into the step structure 122 for interconnection. As shown in FIG. 1, according to some embodiments, the offset of the edge of each adjacent conductor/dielectric layer pair in the stepped structure 122 is nominally the same.

As shown in FIG. 1, each NAND memory string 114 may extend vertically through the inner region of the storage stack layer 120 and include a semiconductor channel 124 and a dielectric layer (also called “storage film”). In some embodiments, the semiconductor channel 124 includes silicon, such as amorphous silicon, polycrystalline silicon, or single crystal silicon. In some embodiments, the storage film is a composite layer, including a tunneling layer 126, a storage layer 128 (also referred to as a "charge trapping/storage layer"), and a barrier layer (not shown). Each NAND memory string 114 may have a cylindrical shape (for example, a cylindrical shape). According to some embodiments, the semiconductor channel 124, the tunneling layer 126, the storage layer 128, and the barrier layer are radially arranged in this order from the center of the pillar toward the outer surface. The tunneling layer 126 may include silicon oxide, silicon oxynitride, or any combination thereof. The storage layer 128 may include silicon nitride, silicon oxynitride, silicon, or any combination thereof. The barrier layer may include silicon oxide, silicon oxynitride, high dielectric constant (high-k) dielectric material, or any combination thereof.

In some embodiments, the NAND memory string 114 also includes a plurality of control gates (each control gate is part of a word line). Each conductor layer 116 in the storage stack layer 120 can be used as a control gate for each storage cell of the NAND memory string 114. Each NAND memory string 114 may include a source selection gate at its upper end and a drain selection gate at its lower end. As used herein, the “upper end” of an element (eg, NAND memory string 114) is the end away from the substrate 102 in the y direction, and the “lower end” of the element (eg, NAND memory string 114) is at It is close to the end of the substrate 102 in the y direction. For each NAND memory string 114, the drain selection gate may be disposed under the source selection gate in the 3D memory device 100.

In some embodiments, the 3D memory device 100 further includes a semiconductor layer 130 disposed on and in contact with the NAND memory strings 114, for example, on the upper end of each NAND memory string 114. The storage stack layer 120 may be disposed under the semiconductor layer 130. The semiconductor layer 130 may be a thinned substrate on which the storage stack layer 120 is formed. In some embodiments, the semiconductor layer 130 includes a plurality of semiconductor plugs 132 electrically isolated by an isolation region (eg, STI). In some embodiments, each semiconductor plug 132 is disposed at the upper end of the corresponding NAND memory string 114 and serves as the source of the corresponding NAND memory string 114, therefore, it can be considered as a corresponding NAND memory string Part of 114. The semiconductor plug 132 may include single crystal silicon. The semiconductor plug 132 may be undoped, partially doped (in the thickness direction and/or width direction), or completely doped with p-type or n-type dopants. In some embodiments, the semiconductor plug 132 may include SiGe, GaAs, Ge, or any other suitable material. In some embodiments, the thickness of the semiconductor layer 130 (and the semiconductor plug 132 therein) is between about 0.1 μm and about 50 μm, for example between 0.1 μm and 50 μm. In some embodiments, the thickness of the semiconductor layer 130 (and the semiconductor plug 132 therein) is between about 0.2 μm and about 5 μm, such as between 0.2 μm and 5 μm (eg, 0.2 μm, 0.3 μm, 0.4 μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 2μm, 3μm, 4μm, 5μm, any range defined by any of these values by the lower end, or in any range defined by any two of these values ).

In some embodiments, the 3D memory device 100 further includes a gate line gap (“GLS”) 134 extending vertically through the storage stack layer 120. The GLS 134 can be used to form a conductor/dielectric layer pair in the storage stack layer 120 through a gate replacement process. In some embodiments, the GLS 134 is first filled with a dielectric material (eg, silicon oxide, silicon nitride, or any combination thereof) to divide the NAND memory string array into different areas (eg, storage fingers or/and Storage block). Then, according to some embodiments, GLS 134 is filled with conductive or/and semiconductor materials (eg, W, Co, polysilicon, or any combination thereof) to electrically control the array common source (ACS).

In some embodiments, the 3D memory device 100 includes elements formed in one or more ILD layers and in contact with elements in the storage stack layer 120 (eg, word lines (eg, conductor layer 116) and NAND memory string 114) Local interconnection. Interconnects are referred to herein as "local interconnects" because they directly contact elements in the storage stack layer 120 to fan out. As used herein, the term "interconnect" can broadly include any suitable type of interconnection, including vertical interconnect access (eg, via) contacts and lateral interconnect lines. The local interconnect may include word line via contacts 136, bit line via contacts 138, and source line via contacts 140. Each local interconnect may include openings (eg, vias or trenches) filled with conductive materials including, but not limited to, W, Co, Cu, Al, silicide, or any combination thereof.

The word line via contact 136 may extend vertically through one or more ILD layers. Each word line via contact 136 may have its lower end in contact with a corresponding conductor layer 116 in the stepped structure 122 of the storage stack layer 120 (eg, at the landing area) to individually address the corresponding word of the 3D memory device 100 Yuan line. In some embodiments, each word line via contact 136 is disposed above the corresponding conductor layer 116. Each bit line via contact 138 may be disposed under the storage stack layer 120 and make its upper end contact the lower end (drain terminal) of the corresponding NAND memory string 114 to individually address the corresponding NAND memory string 114 . According to some embodiments, a plurality of bit line via contacts 138 are respectively disposed under and in contact with the plurality of NAND memory strings 114. As shown in FIG. 1, the word line through-hole contact 136 and the bit line through-hole contact 138 fan out corresponding storage stack elements toward opposite vertical directions (positive y direction and negative y direction). The source line via contact 140 may extend vertically through one or more ILD layers. Each source line via contact 140 may have its lower end in contact with a corresponding semiconductor plug 132 (eg, source) of the NAND memory string 114. In some embodiments, each source line via contact 140 is disposed above the corresponding NAND memory string 114.

Similar to peripheral devices, the storage array element of the 3D memory device 100 may further include an interconnection layer for transmitting and receiving electrical signals to and from the NAND memory string 114. As shown in FIG. 1, the 3D memory device 100 may include an interconnect layer under the NAND memory string 114 (referred to herein as “array interconnect layer 142 ”). The array interconnect layer 142 may include a plurality of interconnects including one or more interconnect lines 144 and via contacts 146 in the ILD layer. In some embodiments, the array interconnect layer 142 includes a plurality of bonding contacts 148 at its bottom surface. The interconnection line 144, the via contact 146 and the bonding contact 148 may include a conductive material, including but not limited to W, Co, Cu, Al, silicide, or any combination thereof. The remaining area at the bottom surface of the array interconnect layer 142 may be formed with a dielectric material, including but not limited to silicon oxide, silicon nitride, silicon oxynitride, low-k dielectric material, or any combination thereof. The conductive material (of the bonding contact 148) and the dielectric material at the bottom surface of the array interconnect layer 142 may be used for hybrid bonding, as described in detail below.

As shown in FIG. 1, another interconnection layer (referred to herein as "BEOL interconnection layer 150") may be disposed above the NAND memory string 114 and the semiconductor layer 130, and may include interconnections, such as one or a plurality of The interconnect line 152 and the via contact 154 in the ILD layer. The BEOL interconnection layer 150 may also include a contact pad 156 and a redistribution layer (not shown) at the top surface of the 3D memory device 100 for wire bonding or/and bonding with the interposer. The BEOL interconnection layer 150 and the array interconnection layer 142 may be formed on opposite sides of the NAND memory string 114. In some embodiments, the interconnection line 152, the via contact 154, and the contact pad 156 in the BEOL interconnection layer 150 may transmit electrical signals between the 3D memory device 100 and external circuits. The BEOL interconnect layer 150 may be electrically connected to the storage stack layer element through local interconnects. As shown in FIG. 1, each word line via contact 136 may have its upper end in contact with the BEOL interconnect layer 150. Similarly, each source line via contact 140 may have its upper end in contact with the BEOL interconnect layer 150. The arrangement and configuration of the stepped structure 122 and the semiconductor layer 130 allow the word line to be fanned out directly through the local interconnect (eg, the word line via contact 136 and the source line via contact 140) and the BEOL interconnect layer 150 ( For example, the conductor layer 116) and the source of the NAND memory string 114 without bypassing the array interconnect layer 142.

In some embodiments, the 3D memory device 100 further includes one or more through-array contacts (TAC, not shown) extending vertically through the storage stack layer 120. Each TAC may extend through the entire storage stack layer 120 (eg, all of the conductor/dielectric layer pairs therein) and have its upper end in contact with the BEOL interconnect layer 150 and its lower end in contact with the array interconnect layer 142. Therefore, the TAC may form an electrical connection between the peripheral interconnection layer 106 and the BEOL interconnection layer 150 and transfer electrical signals from the peripheral devices of the 3D memory device 100 to the BEOL interconnection.

The bonding interface 158 may be formed between the peripheral interconnect layer 106 and the array interconnect layer 142. The bonding contact 112 may be bonded with the bonding contact 148 at the bonding interface 158. As shown in FIG. 1, the peripheral device (for example, the transistor 104) may be placed under the storage array element (for example, the NAND memory string 114) in the 3D memory device 100 after bonding. In the 3D memory device 100, according to some embodiments, the bonding interface 158 is disposed between the storage array element (eg, NAND memory string 114) and the peripheral device (eg, transistor 104). The peripheral interconnect layer 106 may be between the bonding interface 158 and the peripheral device (eg, transistor 104), and the array interconnect layer 142 may be between the bonding interface 158 and the storage array element (eg, NAND memory string 114) between.

In some embodiments, the first including NAND memory string 114, semiconductor layer 130 (eg, thinned substrate), array interconnect layer 142, BEOL interconnect layer 150, and word line via contact 136 The semiconductor structure (eg, storage array element wafer 160) is bonded to the second semiconductor structure (including the substrate 102, peripheral devices (eg, transistor 104), and peripheral interconnect layer 106) at the bonding interface 158 in a face-to-face manner ( For example, peripheral device wafer 162). The array interconnect layer 142 may contact the peripheral interconnect layer 106 at the bonding interface 158. Peripheral device wafer 162 and storage array element wafer 160 can be bonded using hybrid bonding (also called "metal/dielectric hybrid bonding"), which is a direct bonding technique (for example, when no interlayer is used The bottom forms a bond between the surfaces, such as solder or adhesive), and the metal-metal bond and the dielectric material-dielectric material bond can be obtained at the same time. A metal-metal bond can be formed between the bonding contact 148 and the bonding contact 112, and a dielectric material-dielectric material bond can be formed between the dielectric materials at the remaining area at the bonding interface 158 .

FIGS. 2A-2B illustrate a process for forming an exemplary peripheral device wafer according to some embodiments. FIGS. 3A to 3D illustrate a process for forming an exemplary memory array device wafer according to some embodiments. FIGS. 4A to 4F illustrate a process for forming an exemplary 3D memory device in which a storage array element wafer is bonded to a peripheral device wafer according to some embodiments. FIG. 5 is a flowchart of a method 500 for forming an exemplary peripheral device wafer according to some embodiments. FIG. 6 is a flowchart of a method 600 for forming an exemplary storage array element wafer according to some embodiments. FIG. 7 is a flowchart of a method 700 for forming an exemplary 3D memory device according to some embodiments, in which a storage array element wafer is bonded to a peripheral device wafer. Examples of the 3D memory device shown in FIGS. 2 to 7 include the 3D memory device 100 shown in FIG. 1. Figures 2 to 7 will be described together. It should be understood that the operations shown in methods 500, 600, and 700 are not exhaustive, and that other operations may be performed before, after, or between any of the operations exemplified. In addition, some operations may be performed at the same time, or in a different order than that shown in FIGS. 5 to 7.

Referring to FIG. 5, the method 500 starts at operation 502, where peripheral devices are formed on a first substrate. The substrate may be a silicon substrate. As shown in FIG. 2A, peripheral devices are formed on the silicon substrate 202. The peripheral device may include a plurality of transistors 204 formed on the silicon substrate 202. The transistor 204 can be formed by various processes, including but not limited to lithography, dry/wet etching, thin film deposition, thermal growth, implantation, chemical mechanical polishing (CMP), and any other suitable processes. In some embodiments, a doped region (not shown) is formed in the silicon substrate 202 by ion implantation or/and thermal diffusion, which is used, for example, as the source region or/and the drain region of the transistor 204. In some embodiments, isolation regions (eg, STI, not shown) are also formed in the silicon substrate 202 by wet/dry etching and thin film deposition.

The method 500 proceeds to operation 504, as shown in FIG. 5, where a first interconnect layer (eg, a peripheral interconnect layer) is formed over the peripheral device. The peripheral interconnect layer may include one or the first plurality of interconnects in the plurality of ILD layers. The method 500 proceeds to operation 506, as shown in FIG. 5, where a first plurality of bonding contacts are formed at the top surface of the peripheral interconnect layer.

As shown in FIG. 2B, the peripheral interconnection layer 206 may be formed on the transistor 204. Peripheral interconnect layer 206 may include interconnects including MEOL or/and BEOL interconnect lines 208 and via contacts 210 of peripheral device wafers in a plurality of ILD layers to manufacture peripheral devices (eg, transistor 204 ) Electrical connection. Bonding contacts 212 may be formed at the top surface of the peripheral interconnect layer 206 for hybrid bonding. In some embodiments, the peripheral interconnect layer 206 includes a plurality of ILD layers formed by a plurality of processes and interconnections therein. For example, the interconnection line 208, the via contact 210, and the bonding contact 212 may include conductive materials deposited through one or more thin film deposition processes, including, but not limited to, chemical vapor deposition (CVD), physical gas Phase deposition (PVD), atomic layer deposition (ALD), electroplating, electroless plating, or any combination thereof. The process of forming the interconnect 208, the via contact 210, and the bonding contact 212 may also include lithography, CMP, wet/dry etching, or any other suitable process. The ILD layer may include a dielectric material deposited through one or more thin film deposition processes, including, but not limited to, CVD, PVD, ALD, or any combination thereof. The ILD layer and interconnects shown in Figure 2B may be collectively referred to as "interconnect layers" (eg, peripheral interconnect layer 206).

Referring to FIG. 6, method 600 includes operation 602, where a dielectric stack layer is formed on a second substrate. The substrate may be a silicon substrate. The dielectric stack layer may include a plurality of dielectric/sacrificial layer pairs. As shown in FIG. 3A, an isolation region 304 (for example, STI) is formed in the silicon substrate 302 by wet/dry etching and thin film deposition to electrically isolate the silicon plug 306 (for example, a single crystal silicon plug). The silicon plug 306 may be patterned and doped with n-type or p-type dopants using ion implantation or/and thermal diffusion processes. In some embodiments, the thickness of the isolation region 304 and the silicon plug 306 is between about 0.1 μm and about 50 μm, for example between 0.1 μm and 50 μm. In some embodiments, the thickness of the isolation region 304 and the silicon plug 306 is between about 0.2 μm and about 5 μm, such as between 0.2 μm and 5 μm (eg, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, any range defined by any of these values by the lower end, or in any range defined by any two of these values).

As shown in FIG. 3B, a pair of first dielectric layer 310 and second dielectric layer (referred to as “sacrificial layer”) 312 (collectively referred to herein as “dielectric layer pair”) are formed on the silicon substrate 302. The stacked pairs of dielectric layers may form a dielectric stack layer 308. The dielectric stack layer 308 may include alternating stack layers of the sacrificial layer 312 and the dielectric layer 310 different from the sacrificial layer 312. In some embodiments, each dielectric layer pair includes a silicon nitride layer and a silicon oxide layer. In some embodiments, the sacrificial layers 312 may each have the same thickness or have different thicknesses. Similarly, the dielectric layers 310 may each have the same thickness or different thicknesses. The dielectric stack layer 308 may be formed by one or more thin film deposition processes, including, but not limited to, CVD, PVD, ALD, or any combination thereof.

The method 600 proceeds to operation 604, as shown in FIG. 6, where a plurality of memory strings are formed, each memory string extending vertically through the dielectric stack. As shown in FIG. 3C, NAND memory strings 314 are formed on the silicon substrate 302, and each NAND memory string extends vertically through the dielectric stack layer 308. In some embodiments, each NAND memory string 314 may be aligned with the corresponding silicon plug 306. The silicon plug 306 may be part of the NAND memory string 314. In some embodiments, the process of forming the NAND memory string 314 includes forming a semiconductor channel 316 that extends vertically through the dielectric stack layer 308. In some embodiments, the process of forming the NAND memory string 314 further includes forming a composite dielectric layer (storage film) between the semiconductor channel 316 and the plurality of dielectric/sacrificial layer pairs in the dielectric stack layer 308. The storage film may be a combination of a plurality of dielectric layers, including but not limited to a tunneling layer 318, a storage layer 320, and a barrier layer.

The tunneling layer 318 may include a dielectric material, including but not limited to silicon oxide, silicon nitride, silicon oxynitride, or any combination thereof. The storage layer 320 may include a material for storing charges used for memory operations. The storage layer material may include, but is not limited to, silicon nitride, silicon oxynitride, a combination of silicon oxide and silicon nitride, or any combination thereof. The barrier layer may include a dielectric material including, but not limited to, silicon oxide, or a combination of silicon oxide/silicon oxynitride/silicon oxide (ONO). The barrier layer may also include a high-k dielectric layer, such as an aluminum oxide layer. The semiconductor channel 316 and the storage film (including the tunneling layer 318 and the storage layer 320) may be formed by a process such as ALD, CVD, PVD, any other suitable process, or any combination thereof.

The method 600 proceeds to operation 606, as shown in FIG. 6, where a second interconnect layer (eg, an array interconnect layer) is formed over the memory string. The array interconnect layer may include one or a second plurality of interconnects in the ILD layer. The method 600 proceeds to operation 608, as shown in FIG. 6, where a second plurality of bonding contacts are formed at the top surface of the array interconnect layer. As shown in FIG. 3D, the array interconnect layer 322 may be formed over the dielectric stack layer 308 and the NAND memory string 314. The array interconnect layer 322 may include interconnects including interconnect lines 324 and via contacts 326 in one or more ILD layers for transmitting electrical signals to and from the NAND memory string 314 314 transmits electrical signals. In some embodiments, the bit line via contact 321 may be formed in the ILD layer formed above the dielectric stack layer 308 before the array interconnect layer 322 is formed, so that each bit line via contact 321 is at The corresponding NAND memory string 314 is above and in contact with it. Bonding contacts 328 may be formed at the top surface of the array interconnect layer 322 for hybrid bonding.

In some embodiments, the array interconnect layer 322 includes a plurality of ILD layers formed in a plurality of processes and interconnections therein. For example, the interconnection line 324, the via contact 326, and the bonding contact 328 may include conductive materials deposited through one or more thin film deposition processes including, but not limited to, CVD, PVD, ALD, electroplating, and electroless plating Or any combination thereof. The process of forming the interconnect 324, the via contact 326, and the bonding contact 328 may also include lithography, CMP, wet/dry etching, or any other suitable process. The ILD layer may include a dielectric material deposited through one or more thin film deposition processes, including, but not limited to, CVD, PVD, ALD, or any combination thereof. The ILD layer and interconnects shown in the 3D figure may be collectively referred to as "interconnect layers" (eg, array interconnect layer 322).

Referring to FIG. 7, the method 700 includes an operation 702 in which the second substrate on which the memory string is formed is turned upside down. As a result, the second substrate is located above the memory string. The method 700 proceeds to operation 704, as shown in FIG. 7, where the second substrate and the first substrate on which peripheral devices are formed are bonded in a face-to-face manner so that the peripheral interconnection layer is below the array interconnection layer And get in touch with it. The bonding may be a hybrid bonding.

As shown in FIG. 4A, the silicon substrate 302 and the elements formed thereon (for example, the NAND memory string 314) are turned upside down. The array interconnection layer 322 facing downwards will be bonded to the peripheral interconnection layer 206 facing upwards, that is, in a face-to-face manner, so that the array interconnection layer 322 may be in the peripheral interconnection layer 206 in the resulting 3D memory device Above and in contact with it. In some embodiments, the bonding contacts 328 of the array interconnect layer 322 are aligned with the bonding contacts 214 of the peripheral interconnect layer 206 before bonding. As a result, when the silicon substrate 302 is connected to the silicon substrate 202, the bonding contact 328 may be in contact with the bonding contact 214. In some embodiments, a treatment process (eg, plasma treatment, wet treatment, and/or heat treatment) is applied to the bonding surface before bonding. As a result of bonding (eg, hybrid bonding), the bonding contacts 328 and the bonding contacts 214 can be mixed with each other, thereby forming a bonding interface 402 between the array interconnect layer 322 and the peripheral interconnect layer 206, such as Shown in Figure 4B.

The method 700 proceeds to operation 706, as shown in FIG. 7, where the second substrate is thinned. As shown in FIG. 4B, the silicon substrate 302 becomes a single crystal silicon layer 404 (including the silicon plug 306 and surrounding isolation regions) after thinning. In some embodiments, after the thinning process, the single crystal silicon layer 404 (and the silicon plug 306 therein) has a thickness between about 0.1 μm and about 50 μm, such as between 0.1 μm and 50 μm. In some embodiments, the thickness of the single crystal silicon layer 404 (and the silicon plug 306 therein) is between about 0.2 μm and about 5 μm, such as between 0.2 μm and 5 μm (eg, 0.2 μm, 0.3 μm, 0.4 μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 2μm, 3μm, 4μm, 5μm, any range defined by any of these values from the lower end, or in a range defined by any two of these values Any range). The silicon substrate 302 may be thinned by processes including but not limited to wafer grinding, dry etching, wet etching, CMP, any other suitable processes, or any combination thereof.

Method 700 proceeds to operation 708, as shown in FIG. 7, where a stepped structure is formed at the edge of the dielectric stack. The stepped structure may be formed by performing a plurality of trimming etching cycles on the dielectric/sacrificial layer pair toward the first substrate. As shown in FIG. 4C, a stepped structure 406 is formed at the edge of the dielectric stack layer 308. The edges of the dielectric/sacrificial layer pair in the vertical structure (positive y direction) away from the silicon substrate 202 in the stepped structure 406 of the dielectric stack layer 308 are laterally staggered toward the NAND memory string 314. To form the stepped structure 406, the photoresist layer may be patterned to expose a portion of one dielectric/sacrificial layer pair on top of the dielectric/sacrificial layer pair. The patterned photoresist layer can be used as an etch mask to etch the exposed portion of one dielectric/sacrificial layer pair on top of the dielectric/sacrificial layer pair by wet etching or/and dry etching. Any suitable etchant (eg, wet etching or/and dry etching etchant) can be used to remove the entire thickness of the dielectric/sacrificial layer pair on top of the dielectric/sacrificial layer pair (including Sacrificial layer 312 and dielectric layer 310). The thickness of the etch can be controlled by stopping the etch on different materials (eg, silicon nitride and silicon oxide) used in the dielectric/sacrificial layer pair. Etching the exposed portion of a dielectric/sacrificial layer pair on top of the dielectric/sacrificial layer pair can expose a dielectric/sacrificial layer pair on top of the dielectric/sacrificial layer pair section.

The patterned photoresist layer can then be trimmed (eg, often etched gradually and inward from all directions) to expose the other part of the dielectric/sacrificial layer pair on top of the dielectric/sacrificial layer pair. The amount of trimmed photoresist layer can be controlled by the trim rate or/and trim time, and can be directly related to the size of the resulting step structure (eg, determinant). Any suitable etching process may be used, for example, isotropic dry etching or wet etching, to perform trimming of the photoresist layer. Use the trimmed photoresist layer as an etch mask to etch an enlarged exposed portion of the dielectric/sacrificial layer pair on top of the dielectric/sacrificial layer pair and below the dielectric/sacrificial layer pair on top of the dielectric/sacrificial layer pair An exposed portion of a dielectric/sacrificial layer pair to form a stepped structure in the stepped structure 406. Any suitable etchant (eg, wet etching or/and dry etching etchant) can be used to remove the entire thickness of the dielectric/sacrificial layer pair (including the sacrificial layer 312 and Dielectric layer 310). The photoresist layer trimming process is followed by a dielectric/sacrificial layer pair etching process, which is referred to herein as a dielectric/sacrificial layer pair trimming etching cycle.

The trimming-etching cycle of the dielectric/sacrificial layer pair may be repeated toward the silicon substrate 202 (negative y direction) until the etching of the dielectric/sacrificial layer pair at the bottom of the dielectric/sacrificial layer pair is completed. Therefore, a step structure 406 having a plurality of step structures at the edges of the dielectric stack layer 308 can be formed. Due to the repeated trimming-etching cycle of the dielectric/sacrificial layer pair, the dielectric stack layer 308 may have sloped side edges and a top dielectric/sacrificial layer pair shorter than the bottom dielectric/sacrificial layer pair, as shown in FIG. 4C Show.

The method 700 proceeds to operation 710, as shown in FIG. 7, where a storage stack layer is formed under the thinned second substrate by replacing the sacrificial layer in the dielectric/sacrificial layer pair with a plurality of conductor layers. Therefore, the storage stack layer includes a plurality of conductor/dielectric layer pairs. In some embodiments, forming the storage stack layer includes etching an opening through the thinned second substrate and the dielectric/sacrificial layer pair, etching the sacrificial layer in the dielectric/sacrificial layer pair through the opening, and passing through the opening A conductor layer in a conductor/dielectric layer pair is deposited. As a result, a stepped structure can be formed at the edge of the storage stack layer. The edges of the conductor/dielectric layer pair along the vertical direction away from the first substrate in the stepped structure of the storage stack layer may be staggered laterally toward the memory string.

As shown in FIG. 4D, GLS 408 is formed through the dielectric/sacrificial layer pair of single crystal silicon layer 404 and dielectric stack layer 308. GLS 408 may be patterned and etched by wet etching or/and dry etching. Each sacrificial layer 312 of the dielectric stack layer 308 (shown in FIG. 4C) can then be etched through the GLS 408, and a conductor layer 410 can be deposited through the GLS 408. That is, each sacrificial layer 312 of the dielectric stack layer 308 can be replaced with a conductor layer 410, thereby forming a plurality of conductor/dielectric layer pairs in the storage stack layer 412. Replacing the sacrificial layer 312 with the conductor layer 410 may be performed by selectively wet/dry etching the sacrificial layer 312 to the dielectric layer 310 and filling the structure with the conductor layer 410. The conductor layer 410 may include a conductive material, including but not limited to W, Co, Cu, Al, doped silicon, polysilicon, silicide, or any combination thereof. The conductor layer 410 may be filled by a thin film deposition process such as CVD, ALD, any other suitable process, or any combination thereof.

As a result, the NAND memory strings 314 may each extend vertically through the storage stack layer 412. In some embodiments, the conductor layer 410 in the storage stack layer 412 is used to form the select gate and word line of the NAND memory string 314. At least some of the conductor layers 410 in the storage stack layer 412 (eg, in addition to the top and bottom conductor layers 410) may each be used as a word line of the NAND memory string 314. As a result of gate replacement, a stepped structure 414 may be formed at the edge of the storage stack layer 412. The edges of the conductor/dielectric layer pairs in the vertical direction (positive y direction) away from the silicon substrate 202 in the stepped structure 414 of the storage stack layer 412 may be staggered laterally toward the NAND memory string 314.

The method 700 proceeds to operation 712, as shown in FIG. 7, where a local interconnection of the storage stack layer and the memory string is formed. The local interconnect may include a word line via contact formed above the stepped structure of the storage stack layer, and a source line via contact formed above the memory string. As shown in FIG. 4E, the ILD layer 416 may be formed on the single crystal silicon layer 404 by a thin film deposition process of a dielectric material such as CVD, ALD, any other suitable process, or any combination thereof. The source line via contacts 418 may be formed through the ILD layer 416 and contact the silicon plug 306 of the memory string 314, respectively. Each source line via contact 418 may contact its lower end with the upper end of the corresponding NAND memory string 314. According to some embodiments, the word line via contact 420 passes through one or more ILD layers (including the ILD layer 416) and is formed over the stepped structure 414 of the storage stack layer 412. The lower end of the word line via contact 420 may fall on the word line of the NAND memory string 314 (eg, the conductor layer 410) in the ladder structure 414 of the storage stack layer 412, such that each word line via contact 420 is on and in contact with the corresponding conductor layer 410.

In some embodiments, the process of forming the source line via contact 418 and the word line via contact 420 includes using a dry/wet etching process to form the vertical opening, and then using conductive materials and other materials (eg, a barrier layer , Adhesive layer or/and seed layer) filling the opening for conductor filling, bonding or/and other purposes. The source line via contact 418 and the word line via contact 420 may include a conductive material, including but not limited to W, Co, Cu, Al, doped silicon, silicide, or any combination thereof. The openings of source line via contact 418 and word line via contact 420 may be filled with conductive materials and other materials, by ALD, CVD, PVD, electroplating, any other suitable process, or any combination thereof. In some embodiments, GLS 408 may be filled with dielectric materials by CVD, PVD, ALD, any other suitable process, or any combination thereof, including but not limited to silicon oxide, silicon nitride, silicon oxynitride, or any combination thereof.

The method 700 proceeds to operation 714, as shown in FIG. 7, where a third interconnect layer (eg, a BEOL interconnect layer) is formed over the thinned second substrate. The BEOL interconnect layer may include one or a third plurality of interconnects in the ILD layer. As shown in FIG. 4F, the BEOL interconnection layer 422 may be formed on the single crystal silicon layer 404 and the NAND memory string 314. The BEOL interconnection layer 422 may include an interconnection including one or more interconnection lines 424 and via contacts 426 in the ILD layer for transmitting electrical signals to and from the 3D memory device electric signal. In some embodiments, contact pads 428 and a redistribution layer (not shown) may be formed at the top surface of BEOL interconnect layer 422 for wire bonding or/and bonding with the interposer.

In some embodiments, the BEOL interconnection layer 422 includes a plurality of ILD layers formed in a plurality of processes and interconnections therein. For example, the interconnect 424, the via contact 426, and the contact pad 428 may include conductive materials deposited through one or more thin film deposition processes including, but not limited to, CVD, PVD, ALD, electroplating, electroless plating, or any of them combination. The process of forming the interconnect 424, the via contact 426, and the contact pad 428 may also include lithography, CMP, wet/dry etching, or any other suitable process. The ILD layer may include a dielectric material deposited through one or more thin film deposition processes, including, but not limited to, CVD, PVD, ALD, or any combination thereof. The ILD layer and interconnects shown in Figure 4F may be collectively referred to as "interconnect layers" (eg, BEOL interconnect layer 422).

Although not shown, in some embodiments, before bonding, a TAC is formed that extends vertically through the dielectric stack layer 308 and contacts the interconnect in the array interconnect layer 322. After bonding, a via contact can be formed that extends vertically through one or more ILD layers and contacts the TAC so that the BEOL interconnect layer 422 can be electrically connected to the peripheral interconnect layer 206.

According to an aspect of the present disclosure, a method for forming a 3D memory device is disclosed. The peripheral device is formed on the first substrate. A first interconnect layer is formed on the peripheral device on the first substrate. A dielectric stack layer including a plurality of dielectric/sacrificial layer pairs and a plurality of memory strings is formed on the second substrate, and each memory string extends vertically through the dielectric stack layer. A second interconnect layer is formed on the memory string on the second substrate. The first substrate and the second substrate are bonded so that the first interconnect layer is below and in contact with the second interconnect layer. After bonding, the second substrate is thinned. By replacing the sacrificial layer in the dielectric/sacrificial layer pair with a plurality of conductor layers, the storage stack layer is formed under the thinned second substrate and includes a plurality of conductor/dielectric layer pairs.

In some embodiments, after bonding, a stepped structure is formed at the edge of the dielectric stack. According to some embodiments, to form a stepped structure, before forming the storage stack layer, a plurality of trimming etch cycles are performed toward the first substrate pair dielectric/sacrificial layer pair.

In some embodiments, a plurality of first via contacts are formed such that each first via contact is above and in contact with the conductor layer of one conductor/dielectric layer pair of the conductor/dielectric layer pair Layer contact. In some embodiments, a plurality of second via contacts are formed so that each second via contact is on and in contact with one of the memory strings.

In some embodiments, after forming the storage stack layer, a third interconnect layer is formed over the thinned second substrate.

In some embodiments, the bonding includes hybrid bonding. According to some embodiments, in order to bond the first substrate and the second substrate, the second substrate is turned upside down.

In some embodiments, in order to form the storage stack layer, the opening through the thinned second substrate and the plurality of dielectric/sacrificial layer pairs is etched; the sacrificial layer in the plurality of dielectric/sacrificial layer pairs is etched through the opening ; And deposit a plurality of conductor layers in the conductor/dielectric layer pair through the opening.

According to another aspect of the present disclosure, a method for forming a 3D memory device is disclosed. The peripheral device is formed on the first substrate. A first interconnect layer is formed on the peripheral device on the first substrate. A plurality of memory strings each extending vertically are formed on the second substrate. A second interconnect layer is formed on the memory string on the second substrate. The first substrate and the second substrate are bonded so that the first interconnect layer is below and in contact with the second interconnect layer. After bonding, the second substrate is thinned. The storage stack layer is formed under the thinned second substrate and includes a plurality of conductor/dielectric layer pairs. In the stepped structure of the storage stack layer, the edges of the conductor/dielectric layer pair along the vertical direction away from the first substrate are laterally staggered toward the memory string.

In some embodiments, a dielectric stack including a plurality of pairs of dielectric/sacrificial layers is formed before bonding, and the memory string extends vertically through the pairs of dielectric/sacrificial layers. According to some embodiments, in order to form a storage stack layer, a stepped structure is formed at the edge of the dielectric stack layer; and the sacrificial layer in the dielectric/sacrificial layer pair is replaced by a plurality of conductor layers. According to some embodiments, in order to replace the sacrificial layer, the opening through the thinned second substrate and the plurality of dielectric/sacrificial layer pairs is etched; the sacrificial layer in the plurality of dielectric/sacrificial layer pairs is etched through the opening; and Multiple conductor/dielectric layer centered conductor layers are deposited through the opening. In some embodiments, to form a stepped structure, a plurality of trimming etch cycles are performed toward the first substrate pair dielectric/sacrificial layer pair.

In some embodiments, a plurality of first via contacts are formed such that each first via contact is above and in contact with the conductor layer of one conductor/dielectric layer in the conductor/dielectric layer pair contact. In some embodiments, a plurality of second via contacts are formed so that each second via contact is on and in contact with one of the memory strings.

In some embodiments, after forming the storage stack layer, a third interconnect layer is formed over the thinned second substrate.

In some embodiments, the bonding includes hybrid bonding. According to some embodiments, in order to bond the first substrate and the second substrate, the second substrate is turned upside down.

According to yet another aspect of the present disclosure, a method for forming a 3D memory device is disclosed. A plurality of memory strings each extending vertically are formed on the substrate. An interconnect layer is formed on the memory string. Turn the substrate upside down so that the substrate is above the memory string. After turning over, the substrate is thinned. After thinning, the storage stack layer is formed under the thinned substrate and includes a plurality of conductor/dielectric layer pairs. A plurality of first via contacts are formed such that each first via contact is above and in contact with the conductor layer of one conductor/dielectric layer pair of the conductor/dielectric layer pair.

In some embodiments, a plurality of second via contacts are formed after forming the storage stack layer, such that each second via contact is on and in contact with one of the memory strings in the memory string contact.

In some embodiments, a second interconnect layer is formed over the thinned substrate so that the plurality of first and second via contacts are in contact with the second interconnect layer.

In some embodiments, a dielectric stack including a plurality of pairs of dielectric/sacrificial layers is formed before flipping, and the memory string extends vertically through the pairs of dielectric/sacrificial layers. According to some embodiments, in order to form the storage stack layer, a stepped structure is formed at the edge of the dielectric stack layer; and the sacrificial layer in the dielectric/sacrificial layer pair is replaced by a plurality of conductor layers. According to some embodiments, to replace the sacrificial layer, etch through the opening of the thinned substrate and the plurality of dielectric/sacrificial layer pairs; etch the sacrificial layer of the plurality of dielectric/sacrificial layer pairs through the opening; and pass through The opening deposits a plurality of conductor layers in a conductor/dielectric layer pair. In some embodiments, to form a stepped structure, a plurality of trimming etch cycles are performed away from the thinned substrate pair dielectric/sacrificial layer pair.

The above description of specific embodiments will thus reveal the general nature of the present disclosure, enabling others to easily modify or/and adjust such specific embodiments for various applications by applying knowledge within the technical scope of the art, without Excessive experimentation is required without departing from the general concept of this disclosure. Therefore, based on the teachings and guidance presented herein, such adjustments and modifications are intended to be within the meaning and scope of equivalents of the disclosed embodiments. It should be understood that the wording or terminology herein is for illustrative purposes and not for limitation, so that the terminology or wording of this specification will be interpreted by the skilled person in accordance with the teaching and guidance.

The embodiments of the present disclosure have been described above with the help of function building blocks, which exemplify embodiments specifying functions and their relationships. The boundaries of these functional building blocks are arbitrarily defined in this article for the convenience of description. Alternative boundaries can be defined as long as the specified functions and their relationships are properly performed.

The summary and abstract sections may illustrate one or more exemplary embodiments of the present disclosure envisioned by the inventor, but not necessarily all exemplary embodiments, and therefore, it is not intended to limit the present disclosure and the attached patent applications in any way range.

The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, and should be limited only in accordance with the scope of patent applications for the attached invention and their equivalents. The above are only the preferred embodiments of the present invention, and all changes and modifications made in accordance with the scope of the patent application of the present invention shall fall within the scope of the present invention.

100‧‧‧3D memory device 102‧‧‧‧substrate 104‧‧‧transistor 106‧‧‧peripheral interconnect layer 108‧‧‧ interconnect 110 110‧‧‧via contact 112‧‧‧bond contact Dot 114‧‧‧NAND memory string 116‧‧‧conductor layer 118‧‧‧dielectric layer 120‧‧‧storage stack layer 122‧‧‧ ladder structure 124‧‧‧semiconductor channel 126‧‧‧tunnel layer 128‧ ‧‧Storage layer 130‧‧‧Semiconductor layer 132‧‧‧Semiconductor plug 134‧‧‧Gate line gap 136‧‧‧Character line via contact 138‧‧‧Bit line via contact 140‧‧ ‧Source line via contact 142‧‧‧Array interconnect layer 144‧‧‧Interconnect line 146‧‧‧via contact 148‧‧‧bond contact 150‧‧‧BEOL interconnect layer 152‧‧ ‧Interconnect 154‧‧‧Through-hole contact 156‧‧‧Contact pad 158‧‧‧ Bonding interface 160‧‧‧Storage array element chip 162‧‧‧Peripheral device chip 202‧‧‧Silicon substrate 204‧‧ ‧Transistor 206‧‧‧Peripheral interconnect layer 208‧‧‧Interconnect 210 210‧‧‧Through-hole contact 212‧‧‧ Bonding contact 214‧‧‧ Bonding contact 302 ‧‧‧Isolated area 306‧‧‧Silicon plug 308‧‧‧ Dielectric stack 310‧‧‧‧Dielectric layer 312‧‧‧Sacrifice layer 314‧‧‧NAND memory string 316‧‧‧Semiconductor channel 318‧‧ ‧Tunnel layer 320‧‧‧Storage layer 321‧‧‧Bit line via contact 322‧‧‧Array interconnect layer 324‧‧‧Interconnect line 326‧‧‧Through contact 328‧‧‧bond Contact 402‧‧‧ Bonding interface 404‧‧‧Single crystal silicon layer 406‧‧‧Step structure 408‧‧‧GLS410‧‧‧Conductor layer 412‧‧‧Storage stack layer 414‧‧‧Step structure 416‧‧‧ ILD layer 418‧‧‧Source line via contact 422‧‧‧BEOL interconnect layer 424‧‧‧Interconnect line 426‧‧‧via contact 428‧‧‧Contact pad 500‧‧‧Method 502‧‧ ‧Operation 504‧‧‧Operation 506‧‧‧Operation 600‧‧‧Method 602‧‧‧Operation 604‧‧‧Operation 606‧‧‧Operation 608‧‧‧Operation 700‧‧‧Method 702‧‧‧Operation 704‧‧ ‧Operation 706‧‧‧Operation 708‧‧‧Operation 710‧‧‧Operation 712‧‧‧Operation 714‧‧‧Operation

The drawings incorporated herein and constituting a part of the specification show embodiments of the present disclosure, and are used together with the specification to further explain the principles of the present disclosure and enable those skilled in the relevant art to implement and use the present disclosure. Figure 1 shows a cross-section of an exemplary 3D memory device according to some embodiments. FIGS. 2A-2B illustrate a process for forming an exemplary peripheral device wafer according to some embodiments. FIGS. 3A to 3D illustrate a process for forming an exemplary memory array device wafer according to some embodiments. FIGS. 4A to 4F illustrate a process for forming an exemplary 3D memory device in which a storage array element wafer is bonded to a peripheral device wafer according to some embodiments. FIG. 5 is a flowchart of a method for forming an exemplary peripheral device wafer according to some embodiments. FIG. 6 is a flowchart of a method for forming an exemplary storage array element wafer according to some embodiments. FIG. 7 is a flowchart of a method for forming an exemplary 3D memory device according to some embodiments, in which a storage array element wafer is bonded to a peripheral device wafer. The embodiments of the present disclosure will be described with reference to the drawings.

100‧‧‧3D memory device

102‧‧‧Substrate

104‧‧‧Transistor

106‧‧‧Peripheral interconnection layer

108‧‧‧Interconnect

110‧‧‧Through hole contact

112‧‧‧bond contact

114‧‧‧NAND memory string

116‧‧‧Conductor layer

118‧‧‧dielectric layer

120‧‧‧Storage stack

122‧‧‧Ladder structure

124‧‧‧Semiconductor channel

126‧‧‧Tunnel layer

128‧‧‧Storage layer

130‧‧‧Semiconductor layer

132‧‧‧Semiconductor plug

134‧‧‧Gate line gap

136‧‧‧Character line through-hole contact

138‧‧‧bit line through hole contact

140‧‧‧ source line through-hole contact

142‧‧‧Array interconnection layer

144‧‧‧Interconnect

146‧‧‧Through hole contact

148‧‧‧bond contact

150‧‧‧BEOL interconnection layer

152‧‧‧Interconnect

154‧‧‧Through hole contact

156‧‧‧Contact pad

158‧‧‧bond interface

160‧‧‧Storage array element chip

162‧‧‧Peripheral device chip

Claims (20)

A method for forming a three-dimensional (3D) memory device includes: forming a peripheral device on a first substrate; forming a first interconnect layer on the peripheral device on the first substrate; Forming a dielectric stack layer on the bottom, the dielectric stack layer including a plurality of dielectric/sacrificial layer pairs and a plurality of memory strings, each of the memory strings extending vertically through the dielectric stack layer; on the second substrate Forming a second interconnect layer on the memory strings on the top; bonding the first substrate and the second substrate so that the first interconnect layer is below the second interconnect layer and is in contact with the The second interconnect layer contact; thinning the second substrate after the bonding; and forming the storage stack layer in the thinning by replacing the sacrificial layer in the dielectric/sacrificial layer pair with a plurality of conductor layers Under the second substrate and including a plurality of conductor/dielectric layer pairs. The method of claim 1, further comprising forming a stepped structure at the edge of the dielectric stack layer after the bonding. The method of claim 2, wherein forming the stepped structure includes performing a plurality of trimming etch cycles on the dielectric/sacrificial layer pairs toward the first substrate before forming the storage stack layer. The method of claim 1, further comprising forming a plurality of first via contacts, such that each of the first via contacts is a conductor/conductor of the dielectric/pair of the pair of conductors/dielectric layers Above the layer and in contact with the conductor layer. The method of claim 1, further comprising forming a plurality of second through-hole contacts such that each second through-hole contact is on and in contact with the memory string in one of the memory strings contact. The method of claim 1, further comprising forming a third interconnect layer on the thinned second substrate after forming the storage stack layer. The method of claim 1, wherein the bonding includes a hybrid bonding. The method of claim 1, wherein forming the storage stack includes: etching an opening through the thinned second substrate and the dielectric/sacrificial layer pair; etching the dielectric/through the opening/ The sacrificial layers in the sacrificial layer pair; and the conductor layers in the conductor/dielectric layer pairs deposited through the opening. The method of claim 1, wherein bonding the first substrate and the second substrate includes turning the second substrate upside down. A method for forming a three-dimensional (3D) memory device includes: forming a peripheral device on a first substrate; forming a first interconnect layer on the peripheral device on the first substrate; Forming a plurality of memory strings each vertically extending on the bottom; forming a second interconnection layer on the memory strings on the second substrate; bonding the first substrate and the second substrate , So that the first interconnect layer is below the second interconnect layer and in contact with the second interconnect layer; after the bonding, the second substrate is thinned; and the storage stack layer is formed in the thinned Under the second substrate and including a plurality of conductor/dielectric layer pairs, wherein the edges of the conductor/dielectric layer pairs in the vertical structure away from the first substrate in the stepped structure of the storage stack layer The memory strings are staggered laterally toward the memory strings. The method of claim 10, further comprising, before the bonding, forming a dielectric stack layer including a plurality of dielectric/sacrificial layer pairs on the second substrate, the memory strings passing through the dielectric The electric/sacrificial layer pair extends vertically. The method of claim 11, wherein forming the storage stack layers includes: forming the stepped structure at the edge of the dielectric stack layer; and replacing the sacrifice in the dielectric/sacrificial layer pair by a plurality of conductor layers Floor. The method of claim 12, wherein replacing the sacrificial layers comprises: etching the openings through the thinned second substrate and the dielectric/sacrificial layer pair; etching the dielectrics through the openings/ The sacrificial layers in the sacrificial layer pair; and the conductor layers in the conductor/dielectric layer pairs deposited through the opening. The method of claim 12, wherein forming the stepped structure includes performing a plurality of trimming etch cycles for the dielectric/sacrificial layer pairs toward the first substrate. The method of claim 10, further comprising forming a plurality of first via contacts, such that each of the first via contacts is a conductor/conductor of the dielectric/pair of the pair of conductors/dielectric layers Above the layer and in contact with the conductor layer. The method according to claim 10, further comprising forming a plurality of second through-hole contacts such that each second through-hole contact is on and in contact with the memory string in one of the memory strings contact. The method of claim 10, further comprising forming a third interconnect layer on the thinned second substrate after forming the storage stack layer. The method of claim 10, wherein the bonding includes a hybrid bonding. The method of claim 10, wherein bonding the first substrate and the second substrate includes turning the second substrate upside down. A method for forming a three-dimensional (3D) memory device, comprising: forming a plurality of memory strings each vertically extending on a substrate; forming an interconnection layer on the memory strings; and up and down the substrate Flipping, so that the substrate is located on the memory strings; after the flipping, the substrate is thinned; after the thinning, the storage stack layer is formed under the thinned substrate and includes a plurality of conductors /Dielectric layer pair; and forming a plurality of first through-hole contacts such that each of the first through-hole contacts is on the conductor layer of one conductor/dielectric layer pair of the conductor/dielectric layer pairs and Contact with this conductor layer.

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